I think the thing people often misunderstand about piston clearance, is that pistons are designed and machined undersized for a given bore.

If you have a 4" bore. The piston doesn't come in at 4" and you bore/hone for .005 of clearance. The piston is designed and machined to come in at 3.995" to give you .005" of clearance in a 4" bore.

So just because an old block used pistons with a ton of clearance, doesn't mean that you can't put a hypereutectic in it. If the bore is only over .001", it will only ad point .001" into the new piston clearance regardless of what brand/type of piston that was in the motor.

Of course pistons need to be checked for size, but machining and quality is so good now, you don't really have to worry about it.

I built a 340 with hypereutectic pistons in it a LONG time ago. It's got 500~600 passes, and God knows how many street miles on it.

I'd use them again for a street/strip build in a heartbeat.